1. Field of the Invention
The present invention relates to a self-expanding occlusion device for occluding an atrial auricula including a braiding of thin wires or threads given a suitable form by means of a molding and heat treatment procedure, whereby the occlusion device has a rear proximal retention area and a front distal retention area and whereby the ends of the wires or threads converge in a holder in the distal retention area. The occlusion device moreover has a center section between the proximal and the distal retention area.
The occlusion device is configured in such a manner that it can be introduced into the body of a patient in collapsed state and positioned in the atrial auricula of the patient in a minimally invasive procedure using a catheter. The invention furthermore relates to a method for the production of such an occlusion device.
2. Description of the Related Art
The principle behind this type of occlusion device is known to at least some extent in medical technology. For example, an occlusion device for treating septum defects is known from DE 10 338 702 of Aug. 22, 2003, consisting of a braiding of thin wires or threads and given a suitable profile in a molding and heat treatment process. The known occlusion device has a proximal retention area which is particularly distinctly flat, a distal retention area, and a cylindrical crosspiece between the proximal and distal retention areas. The ends of the wires forming the braiding converge into a holder in the distal retention area. This structural design thus allows the two retention areas of the known occlusion device to position on the two sides of a shunt to be occluded in a septum, usually by means of an intravascular surgical procedure, while the crosspiece transverses the shunt.
Medical technology has long endeavored to be able to occlude septal defects, for instance atrioseptal defects, by means of non-surgical transvenous catheter procedures, in other words, without having to perform an operation in the literal sense. Various different occlusion systems have been proposed to this end, each with their own pros and cons, without any one specific occlusion system having yet become widely accepted.
In making reference to these different systems, the following will use the terms “occluder” or “occlusion device.” In all interventional occlusion systems, a self-expanding umbrella system is introduced transvenously into a defect to be occluded in a septum. This type of system might include two umbrellas: one, for example, positioned at the distal side of the septum (i.e. the side furthest from the median plane of the body/heart) and one at the proximal side of the septum (i.e. the side closer to the median plane of the body), whereby the two umbrella prostheses are subsequently secured to a double umbrella in the septal defect. Thus, in the assembled state, the occlusion system usually consists of two clamped umbrellas connected to one another by means of a short bolt transversing the defect.
However, a disadvantage to such prior art occlusion devices turns out to be the relatively complicated, difficult and complex implantation procedure. Apart from the complicated implantation of the occlusion system in the septal defect to be occluded, the umbrellas utilized are susceptible to material fatigue along with fragment fracture. Furthermore, thromboembolic complications are frequently to be anticipated.
In order to enable the inventive occlusion device to be introduced by means of a surgical insertion instrument and/or guidewire, a holder is provided at the end of the distal retention area for engaging with the insertion instrument and/or guidewire. It is thereby intended that this engagement can be readily disengaged after positioning the occlusion device in the defect. For example, it is possible to devise the braiding at the end of the distal retention area of the occlusion device in such a manner so as to create an internal threading in the holder to engage with the insertion instrument. Of course, other embodiments are naturally also conceivable.
With another type of occlusion device, the so-called Lock-Clamshell umbrella system, two stainless steel preferably Dacron-covered umbrellas are provided, each stabilized by four arms. This type of occluder is implanted into the patient through a vein. However, seen as problematic with the Lock-Clamshell occluder is the fact that the insertion instruments necessary to implant the device need to be of relatively large size. A further disadvantage seen with other systems, for example the Amplatz occluder, is that many different occluder sizes are needed in order to cope with the respective dimensions of the septal defects to be occluded. It thus turns out that the umbrellas do not flatten out completely in the inserted state if the length or the diameter of the crosspiece inserted into the defect is not of an optimum match. This results in incomplete endothelialization. It has furthermore been shown that many of the systems implanted into patients' bodies exhibit material fatigue and fractures in the metallic structures due to the substantial mechanical stresses over a longer period. This is especially the case given permanent stress between an implant and the septum.
In order to overcome these disadvantages, self-centering occlusion devices have been developed which are inserted into the body of the patient and introduced into the septal defect to be occluded by way of a minimally invasive procedure, for example using a catheter and guidewires. Their design is based on the principle that the occlusion device can be tapered to the dimensions of the insertion instrument/catheter used for the intravascular procedure. Such a tapered occlusion device is then introduced by catheter into the septal defect to be occluded, respectively into the shunt of the septum defect to be occluded. The occluder is then discharged from the catheter, upon which the self-expanding umbrellas, retention plates respectively, subsequently unfold against the two sides of the septum. The umbrellas in turn comprise fabric inserts made from or covered by, for example, Dacron, with which the defect/shunt is occluded. The implants remaining in the body are more or less completely ingrown by the body's own tissue after a few weeks or months.
An example of a self-centering occlusion device of the type specified is known from WO 99/12478 A1, which is a further development of the occlusion device known as the “Amplatz occluder” in accordance with U.S. Pat. No. 5,725,552. Same consists of a braiding of a plurality of fine, intertwined nitinol wire strands in the shape of a yo-yo. Each braiding is produced in its original form as a rounded braiding having loose wire ends both at its leading end (its proximal side, respectively) as well as at its trailing end (its distal side, respectively). During the subsequent processing of the rounded braiding, each of these loose ends must then be bundled into a sleeve and welded together. After the appropriate processing, both the proximal as well as the distal side of the finished occluder exhibit a protruding collar. Dacron patches are sewn into the distal and proximal retention umbrellas and the interposed crosspiece. Because of the memory effect exhibited by the nitinol material used, the two retention umbrellas unfold by themselves upon exiting the catheter, initially in a balloon-like intermediate stage, whereby the retention umbrellas ultimately positioned on the two sides of the septum eventually assume a more or less flattened form. The crosspiece centers itself automatically into the shunt to be occluded as the umbrellas unfold.
Yet embolic-related problems can arise with an inserted implant due to the protruding collar at the proximal retention area of the occluder, consecutive embolization in particular. Such embolic-related problems arise in particular in cases of patients suffering from so-called atrial fibrillation. Atrial fibrillation is a condition in which the atria of the heart experiences frequent electrical discharge, leading to the atria not contracting. One consequence of this lack of contraction to the atria of the heart is that there is no effective delivery or mixing of the blood and thrombi can form in the atrium. A considerable risk of thrombi developing in an atrium in consequence of atrial fibrillation is that such thrombi can be carried along in the bloodstream and enter the arterial circulation. Strokes are an especially frequent consequence of such embolization, occurring at a rate of roughly 5% per year in patients with atrial fibrillation when not treated chronically with so-called dicumerol to inhibit blood clots. However, effecting the inhibition of blood clots with so-called dicumerol is likewise not without risk. Since the side effects of dicumerol treatment include increased bleeding, contraindications for this treatment arise for approximately 20% of all patients with atrial fibrillation and patients also have to come to terms with the risk of stroke when weighing the hemorrhage/stroke risks.
In the great majority of cases, thrombi forming in the atrium of the heart develop in the so-called atrial auricula. The atrial auricula are appendages found in the atrium of the human heart. The right atrial auricula is situated near the aorta ascendens, the left near the large pulmonary artery. Blood clots which could potentially lead to strokes develop most frequently in the left atrial auricula in patients with atrial fibrillation.
Because of the risks and problems cited in connection with the above-described formation of thrombi in the atrial auricula, the task facing the present invention is that of providing an occlusion device which can be used to occlude the atrial auricula of the left atrium in order to significantly reduce the formation of thrombi coupled with the risk of stroke. To be provided in particular is an occlusion device with which the risk of stroke is also reduced for those patients for whom inhibiting blood clots with dicumerol (so-called anticoagulation) is contraindicated due to bleeding tendencies.